package com.lgd.design.spring;

import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.stereotype.Service;

/**
 * spring 上下文管理，用于获取bean
 */
@Service
public class SpringUtil implements ApplicationContextAware {
    public static ApplicationContext applicationContext;
    /**
     * 实现ApplicationContextAware接口的context注入函数, 将其存入静态变量.
     */
    @Override
    public void setApplicationContext(ApplicationContext applicationContext) {
        SpringUtil.applicationContext = applicationContext;
    }

    /**
     * 取得存储在静态变量中的ApplicationContext.
     */
    public static ApplicationContext getApplicationContext() {
        checkApplicationContext();
        return SpringUtil.applicationContext;
    }

    /**
     * 从静态变量ApplicationContext中取得Bean, 自动转型为所赋值对象的类型.
     */
    public static <T> T getBean(String name) {
        checkApplicationContext();
        try {
            return (T) SpringUtil.applicationContext.getBean(name);
        } catch (Exception t) {
            return null;
        }

    }

    /**
     * 从静态变量ApplicationContext中取得Bean, 自动转型为所赋值对象的类型.
     */
    public static <T> T getBean(Class<T> clazz) {
        checkApplicationContext();
        try {
            return (T) SpringUtil.applicationContext.getBean(clazz);
        } catch (Exception t) {
            return null;
        }
    }

    private static void checkApplicationContext() {
        if (SpringUtil.applicationContext == null) {
            throw new IllegalStateException("applicaitonContext未注入,请在applicationContext.xml中定义SpringContextHolder");
        }
    }
}